Conventionally, as a device for causing particle matters, which become items-to-be-sorted, to flow down and irradiating the flowing-down particle matters with light, detecting color difference or brightness difference by sensors to detect unacceptable items, which are discolored to colors different from colors of acceptable items, or foreign matters, and distinguishing the unacceptable items or foreign matters from the flow of acceptable items to eliminate thereof, a color sorter has been known (for example, refer to Patent Literature 1).
This kind of color sorter is based on a principle that the items-to-be-sorted are irradiated with light from a light source, color difference, brightness difference or the like of reflected light from the items-to-be-sorted or light transmitted through the items-to-be-sorted is detected by a sensor, and based on the color difference or brightness difference, unacceptable items or foreign matters admixed to the items-to-be-sorted are immediately eliminated by an ejector. As a sensor to be adopted, to increase sorting yield, a line sensor configured with a line CCD, which is linear and capable of simultaneous detecting, is used in many cases; as a light source for a sensor like this, in a conventional color sorter, a fluorescent lamp of a straight tube or an array of many halogen bulbs or LED elements has been used (for example, refer to Patent Literature 2, FIG. 9).
Then, the sorter is configured to set plural straight tube fluorescent lamps or linear LED elements with different wavelengths in accordance with the items-to-be-sorted or foreign matters to be the target in the optical detection part, to thereby illuminate each of a side on which the items-to-be-sorted, such as grains, flow down and a proximity of a background, such as a reflective plate; therefore, conventionally, there has been a need for installing plural illumination means in the optical detection part (refer to Patent Literature 2, paragraph 0043, FIG. 4).
Moreover, this kind of color sorter is based on a principle that the items-to-be-sorted are irradiated with light from a light source, color difference, brightness difference or the like of reflected light from the items-to-be-sorted or transmitted light through the items-to-be-sorted is detected by a sensor, and based on the color difference or brightness difference, unacceptable items or foreign matters admixed to the items-to-be-sorted are immediately eliminated by an ejector. As a sensor to be adopted, to increase sorting yield, a line sensor configured with a line CCD, which is linear and capable of simultaneous detecting, is used in many cases; as a light source for a sensor like this, in a conventional color sorter, a fluorescent lamp of a straight tube or an array of many halogen bulbs or LED elements has been used (for example, refer to Patent Literature 3, FIG. 9).